Aerofoil end form



JL v. MARTIN AEROFOIL END FORM origial Filed April 18, 1918'HIIIIIIIIIIIIIIIIIII IIIII INVENTOR w %%Z;`L

Patented Apr. 29, i924..

- rar JAMES V. MARTIN, VOIFl GARDEN CITY, NEW YORK.

AEROFOIL END FORM.

@riginal application led April 18, 1918,. Serial No. 229,664. Dividedand this application vled January 3, 1923. Serial No. 611,811.

T o all whom it may concern:

Be it known that I, JAMES V. MARTIN, a citizen of the United `States,residing at Garden City, in the'county of Nassau and the State of NewYork, have invented a new and useful Aerofoil End Form, of which thefollowing is a' specification.

This invention relates to improvements in aircraft construction and moreparticularly to the novel construction of the aerofoil, exemplifiedherein as a rudder, whereby the wind resistance is reduced and theconstruction simplified.

rlhis is a division of my copending application for shock absorbingrudder, Serial No. 229,664, and relates especially to those features ofthe original application which have been regarded by the Patent Oiice asdistinct inventions.

A further object of my invention is to reduce the air turbulence causedby the presently employed gap between aeroplane controls and the partstowhich they are hinged; the invention consists in the combination,construction and arrangement of parts herein set forth and moreparticularly pointed out in the appended claims.

Heretofore it has been customary to taper down the camber of theaerofoil near the i end and to round the end in plan form: In

the drawing, which is lnerely illustrative of the invention, a simpleand eflicient aerofoil cap or end form is shown which greatly reducesthe air turbulence around the aerofoil ends and is of such simpleconstruction that it may be made up separatelyas a unit and attached tothe aerofoil after the aerofoil framework is otherwise completed.

As shown in the drawing, A indicates the tail end of the fuselage of anaeroplane and B indicates the usual horizontal tail plane or altituderudder, which has end forms such as that indicated by 5 on rudder 1. Onthe extreme end or rear strut of the fuselage a rudder 1 is hinged onrudder post 2 by fuselage pivot supports 3. The rudder 1 is ofstreamline contour, as shown in cross-section in Fig. 2, with thin sidewalls 4 of double convex form, and top and bottom walls 5 having convexouter surfaces; the usual ribs, one of which can be seen in Fig. 1 wherethe aerofoil surface is broken away, hold the aerofoil form of therudder while the rudder post functions in place of the usual lwing sparof an aerofoil; thus providing a hollow structure which is very li htyet affords great strength. The leadinge ge of the rudder aerofoil isnotched so that the top and bottom portions thereof overlap the rear endof the fuselage forming balanced portions and the rudder post is locatedapproximately one third the rudder cord length from the leading edge. 6indicates the lower extremity of the rudder post, 7 a slotl or openingin the rudder. bottom for the accommodation of a skid 8 ivoted at 9 andprovided with rubber shoc absorber at 10; 11 is a streamline attached'to skid 8. The rudder is controlled from the pilots position by means ofthe usual control wires 12 to arms 13, While the horizontal rudder fla 1is controlled by the torque tube 3' indlcated by dotted circle andoperated by means concealed within the fuselage cover. The forwardportion of the horizontal rudder 1s rigid with the fuselage structureaccording to usual practice and has end forms corresponding to the topaerofoil form of the rudder.

An aerofoil is any shape projected through the air for an aerodynamicreaction, and there are generall three sorts or kinds of aerofoilsemployedY chosen -to illustrate my invention as employed upon two of theaeroplane controls, i. e. the directional or rudder control and thelongitudinal or horizontal rudder control, but as shown in my otherapplications for patent, Serials 254,233 and 294,466 and 204,602, thesame double convex aerofoil type can be employed to advantagefor lateralor aileron control and for the main wing and also for the propellerblade.

As shown in Fig. 1, l have eliminated the crackwhich in practice hasheretofore created air turbulence between the aeroplane controls such asailerons and rudders and the rigid aeroplane parts such as wings andfuselage to which these controls are usually attached; for this purposel have made the outer skin of the control surface continuous with therigid portion of the aeroplane to which it is hinged, as illustrated at14 of horizontal rudder B in Fig. 1, and to permit free movement of thecontrol l employ elas-` tic material like dentists rubber to bridge thegap from'the fabric of the control as shown by dotted lines 14 of rudder1 to the fabric of rigid portion shown as fuselage A..

upon an aeroplane, propelling, maintaining and controlling. Ihave Wherefabric is displaced by metal covering sheet aluminumiinay be substitutedfor the rubber, in which case'only the forward edge of the aluminumsheet would be attached to the aeroplane and the rear edge allowed toslide over the surface of the control as it moves about its axis.

My wind tunnel experiments u on aero foils have indicated that gaps orreaks in an aerofoil surface/seriously interfere with the eiiiciency ofthe aerofoil and therefore I have shown means of closing the gaps Where`aerofoils used as controls are hinged and I have also shown an im rovedforni of aeroaerofoil provided with an aerofoil end form ofsubstantially lparabolic shape along a con` siderable portion of itsfore and aft contour 80 and afsubstantially half round form in crosssection.

' 3. An aerofoil end form comprising a substantially strai ht o ortionin contact with the said aerofoiI an a round transverse section taperingin sizey from a small section at' the leading and trailin edges to amaximum at approximately one t ird the aerofoil cod'` length from theleading edge,

4. In an aircraft, an aerofoil end form of substantially half roundshape in sections transverse to. the line of iii ht and-said sectionsgradually increasing 1n radius from a minimum att ing ed es'toa maximumat'approximately one third the aerofoil cord length from .its leadingedge. f

5.f In combination with the rigid portion i of an aircraft, an aircraftcontrolling aeroe aerofoilleading and trail-A mesma foil hinged thereto,said aerofoil aving an end form increasing 1n size of transverse sectionto a maximum at one third distancefrom its rforward part and forming asubstantially continuous streamline with the external surface of saidrigid portion.

6. In combination with an aeroplane fuselage an aircraft rudder controlcomprising a double convex form of aerofoil internally braced andjournalled to turn about an axis located at its approximate greatestcamber,

said/ rudder forming a complementar part of the rear streamline of thesaid fuse age.

selage having a relatively -blunt stern portion providedI with a whollyinternally braced horizontal aerofoil, a rudder fitted to rearward ofsaid blunt portion, journalled thereto and forming a streamlinetherefor.

8. In an aeroplane, aerofoils converging forwardly at their ends andsaid ends pro# vided with end forms having` half round 4 cross sections.

7. In combination with an aeroplanafu- 9. The combination with anaeroplane fuselage having a comparatively blilmI-.rear"I..;`l

end, a rudder having a relativel thick-Iper` tion journalled to saidrear en and forming a substantial streamline continuation of tlieexternal surface of the said fuselage.l

10. In combination with the rear portion of an aeroplane fuselage, adouble convex horizontal aerofoil with its forwardfportion rigidlysecured to said fuselage and its rear portion journalled to said forwardportion, and a rudder aerofoil approximately at right an les` to thefirst said aerofoil and said rud er aerofoil-'complementing the rearstreamline of the said fusela 11. Anaerofoil for 'aeropnes having Aa.com aratively sharp leading edge, portions of t e aerofoil surface lyingon both sides of a straight line from said-'aerofoils leading andtrailing ,edges and an end form of said aerofoil comparatively blunt insections transverse to the line of'flight, but curved in a fore and aftdirection.

t ,im S V. MARTIN.

